Problem: 4 erasers cost $5.96. Which equation would help determine the cost of 12 erasers?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. If we let $x$ represent the cost of 12 erasers, we have the following proportion: $\dfrac{x}{12}$ We have to pay $5.96 for 4 erasers, and that can be written as a proportion: $\dfrac{\$5.96}{4}$ Since the price per eraser stays the same, these two proportions are equivalent. $\dfrac{x}{12} = \dfrac{\$5.96}{4}$